Shale oil, because of its manner of formation, its history and its origin contains high concentrations of trace arsenic compounds. Coal also contains relatively large amounts of arsenic but generally less than shale oil. Other petroliferous deposits generally contain some arsenic but contain greater amounts of other metals and/or metalloids and less arsenic than shale or coal. The ever decreasing supply of conventional petroleum and reserves is forcing us to consider oil shale, heavy petroleum and other petroliferous deposits in lieu of the declining traditional petroleum supplies.
In the refining of petroleum, shale oil, SRC, or other petroliferous derived liquid, catalysts are employed that are readily poisoned by trace metals such as arsenic, nickel and vanadium which are naturally present in the liquid. Examples and particularly sensitive catalysts are those in hydrogenation operations such as hydrocracking and hydrotreating or hydrofinishing catalysts. Such catalysts are very expensive and under normal circumstances can be expected to, and economics require that they perform efficiently for very long periods of time. Typical durations of such long catalyst lives are two and three years. The catalyst load in a reactor of refining size varies, but with refining capacities frequently exceeding 50,000 Bbl/day, can easily exceed several hundred thousand pounds. At present the most commercially acceptable method of protecting hydroprocessing catalyst is by placing a sacrificial bed of similar material (eg. Ni-Mo) or guard case ahead of such catalyst beds. Thus an alternative and economically acceptable method of protecting and preserving these and other refining catalysts from poisoning must be found if sources high in arsenic such as shales, coal and heavy petroleum crudes are to be used to supply significant quantities of our energy needs.
In addition to the foregoing problems, waste water is produced by oil shale retorting. These waste waters originate from mineral dehydration, combustion, groundwater seepage, and steam and moisture required in the input gas. Due to intimate contact with the shale and shale oils, these constitute a leachate containing various of the trace metals and metalloids in one form or another. The shortage of water, particularly in the western areas of the U.S. where the largest and richer deposits of shale is found, makes it important that toxic materials such as arsenic be removed from water effluent from oil shale retorting.
Accordingly, it is a principal object of the present invention to provide an effective method of removing arsenic from liquids derived from petroliferous deposits.
It is another object to provide an effective method of removing various arsenic compounds from shale oils.
It is an important object to provide an efficient, economical process for not only removing arsenic compounds from petroliferous derived liquids, but for regenerating the arsenic binding or removing agent for repeated reuse.
Yet, another object is to provide a method of removing arsenic compounds in a fashion whereby separation from the petroliferous derived liquid can be achieved in a facile, efficient and economical manner.
Still another object is to provide a method of removing arsenic compounds in their various forms (i.e. as both organic or inorganic compounds) from petroliferous derived liquids.
Other objects and advantages of the present invention will become apparent or be realized from the description herein taken as a whole or from practicing the invention.